This invention relates to a light source device for an endoscope and in particular to a light source device using an electronic flash tube.
Recently, a light source device for an endoscope system which incorporates an electronic flash tube or a strobe tube therein has been developed. The amount of light emission of the strobe tube has to be changed according to a foreground subject, for example, a near- or far-distant subject. The amount of light emission is controlled by the following methods.
(1) A plurality of main capacitors are connected to the strobe tube and the number of main capacitors is selected according to the amount of light emission.
(2) A resistor is connected to the strobe tube, thereby adjusting a dissipation power of the strobe tube.
(3) The light emission time of the strobe tube is controlled by a timer.
In the first method (1), a number of main capacitors are required and, moreover, an elaborate and expensive switch is necessary for selecting these main capacitors. The second method (2) requires a plurality of larger-sized resistors, making the device bulkier. Furthermore, an elaborate switch is required for selecting these resistors. In the third method (3), since the light emission time of the strobe tube is very short, an amount of light varies greatly with a slight variation of a timer.
It is accordingly an object of this invention to provide an inexpensive, smaller-sized light source device for an endoscope which can readily effect an accurate light amount adjustment.